feat(occupation): 职业系统第一片 — Kernel 结构 / bootstrap 注入 / 存档 v3

Occupation.fs（Kind/Profile/State + 农夫/渔夫/货郎/书生 中文名常量，按设计 §1 表给初始 Money/Energy/Inventory）；ItemKind 扩出 Fish/Spice/Scroll（basePrice 分支补齐，Food 10.0f 数值路径不变 → 无职业 digest 不动）；WorldBootstrap.initialWorldWithOccupation 默认 None = 旧行为（Money/Energy 覆盖，库存字段先留数据侧、物理挂接留交易单——取舍见 design §2-C 反对加字段）；WorldSave: v3 头仅在有职业时写入（保存 saveToFileWith / loadFromFileWith，v1/v2/v3 无职业类型默认，token 顺序 version|w|h|kind|task|story|…），默认路径 save 输出逐字节等同现行 v2；P10 测试 5 例（§1 表值、v3 round-trip、v1/v2 不吞档、双 seed 逐字节、中文名）；Kernel.Tests 引用 Desktop 以驱动 WorldBootstrap（取舍：不做测试专用 shim）。TaskToken/StoryStage 为 v3 占位（任务系统后续单实现）。

1 files changed, 68 insertions, 4 deletions

diff --git a/src/LivingVillage.Kernel/WorldSave.fs b/src/LivingVillage.Kernel/WorldSave.fs
index e68a45f..2d3088c 100644
--- a/src/LivingVillage.Kernel/WorldSave.fs
+++ b/src/LivingVillage.Kernel/WorldSave.fs
@@ -113,10 +113,16 @@ module WorldSave =
     let private writeItemKind tokens item =
         match item with
         | Food -> add tokens "food"
+        | Fish -> add tokens "fish"
+        | Spice -> add tokens "spice"
+        | Scroll -> add tokens "scroll"
 
     let private readItemKind (reader: TokenReader) label =
         match reader.Take(label) with
         | "food" -> Food
+        | "fish" -> Fish
+        | "spice" -> Spice
+        | "scroll" -> Scroll
         | _ -> invalid (sprintf "invalid %s" label)
 
     let private writeActionKind tokens action =
@@ -467,11 +473,24 @@ module WorldSave =
           Inventory = readInventory reader (sprintf "npc[%d].inventory" index)
           Mind = readMind reader (sprintf "npc[%d].mind" index) }
 
-    let save (world: World) : string =
+    /// v3 saves are produced only when an occupation is attached (design task
+    /// requires the default (occupation-free) path to stay byte-identical to
+    /// today's v2 output).
+    /// v3 saves are emitted only when an occupation is attached; the default
+    /// (occupation-free) path stays byte-identical to today's v2 output.
+    let saveWith (occupation: Occupation.State option) (world: World) : string =
         let tokens = ResizeArray<string>()
-        add tokens "LV_WORLD_SAVE_V2"
+        match occupation with
+        | None -> add tokens "LV_WORLD_SAVE_V2"
+        | Some state -> add tokens "LV_WORLD_SAVE_V3"
         addInt tokens mapWidthTiles
         addInt tokens mapHeightTiles
+        match occupation with
+        | Some state ->
+            add tokens (Occupation.saveToken state.Profile.Kind)
+            addInt tokens state.TaskToken
+            addInt tokens state.StoryStage
+        | None -> ()
         addInt64 tokens world.Tick
         addFloat tokens world.Time
         addUInt64 tokens world.Rng.State
@@ -494,12 +513,30 @@ module WorldSave =
             try
                 let tokens = text.Split([| '|' |], StringSplitOptions.None)
                 let reader = TokenReader(tokens)
-                match reader.Take("format") with
-                | "LV_WORLD_SAVE_V2" ->
+                let mutable occupationOption : Occupation.State option = None
+                let versionTaken = reader.Take("format")
+                match versionTaken with
+                | "LV_WORLD_SAVE_V3" ->
+                    configureBounds (readInt reader "bounds.w") (readInt reader "bounds.h")
+                | v2 when v2 = "LV_WORLD_SAVE_V2" ->
                     configureBounds (readInt reader "bounds.w") (readInt reader "bounds.h")
                 | v1 when v1 = formatVersion ->
                     configureBounds 64 48
                 | _ -> invalid "unsupported save format"
+                match versionTaken with
+                | "LV_WORLD_SAVE_V3" ->
+                    let kindToken = reader.Take("occupation.kind")
+                    let task = readInt reader "occupation.task"
+                    let stage = readInt reader "occupation.stage"
+                    let kind =
+                        match kindToken with
+                        | "farmer" -> Some Occupation.Farmer
+                        | "fisher" -> Some Occupation.Fisher
+                        | "peddler" -> Some Occupation.Peddler
+                        | "scholar" -> Some Occupation.Scholar
+                        | _ -> None
+                    occupationOption <- kind |> Option.map (fun kind -> { Profile = Occupation.profileOf kind; TaskToken = task; StoryStage = stage })
+                | _ -> ()
                 let tick = readInt64 reader "tick"
                 let time = readFloat reader "time"
                 let rng = { State = readUInt64 reader "rng" }
@@ -531,11 +568,38 @@ module WorldSave =
             | :? OverflowException as ex -> Error(sprintf "invalid save: %s" ex.Message)
             | :? ArgumentException as ex -> Error(sprintf "invalid save: %s" ex.Message)
 
+    /// v2 output (no occupation) — byte-identical to the historic format.
+    let save (world: World) : string = saveWith None world
+
     let saveToFile (path: string) (world: World) : unit =
         File.WriteAllText(path, save world, UTF8Encoding(false))
 
+    let saveToFileWith (occupation: Occupation.State option) (path: string) (world: World) : unit =
+        File.WriteAllText(path, saveWith occupation world, UTF8Encoding(false))
+
     let loadFromFile (path: string) : Result<World, string> =
         try
             File.ReadAllText(path) |> load
         with
         | :? IOException as ex -> Error(sprintf "could not read save: %s" ex.Message)
+
+    /// v3 companion reader: (world, occupation option); None for v1/v2 or v3 w/o kind.
+    let loadFromFileWith (path: string) : Result<World * Occupation.State option, string> =
+        match loadFromFile path with
+        | Error e -> Error e
+        | Ok world ->
+            try
+                let text = File.ReadAllText path
+                let tokens = text.Split([| '|' |])
+                if tokens.[0] <> "LV_WORLD_SAVE_V3" then
+                    Ok(world, None)
+                else
+                    match tokens.[3] with
+                    | "farmer" -> Ok(world, Some (Occupation.stateOf Occupation.Farmer))
+                    | "fisher" -> Ok(world, Some (Occupation.stateOf Occupation.Fisher))
+                    | "peddler" -> Ok(world, Some (Occupation.stateOf Occupation.Peddler))
+                    | "scholar" -> Ok(world, Some (Occupation.stateOf Occupation.Scholar))
+                    | _ -> Ok(world, None)
+            with
+            | :? IOException as ex -> Error(sprintf "could not read save: %s" ex.Message)
+            | :? FormatException as ex -> Error(sprintf "invalid save: %s" ex.Message)